An electromagnet with a movable armature is disclosed in German Utility Patent No. 1,850,887. The bearing ring is configured of one part and is slotted so that the bearing ring can be spread apart or bent for the assembly process. The spreading apart or bending of the ring is indispensable. There is no other possible way of fitting the bearing ring into the respective annular groove of the piston armature when the bearing ring has dimensions that hold it against axial movement on the piston armature by engagement with the annular groove.
With conventional magnets, a costly material with high elasticity properties must be provided for the bearing ring. Additionally, danger exists that an outside coating of a slippery material on the bearing ring can be torn during assembly or can be flattened out when the ring is spread apart or bent.